<!DOCTYPE html>
<html lang="en" xmlns:v-text="http://www.w3.org/1999/xhtml" xmlns:v-model="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="http://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>
<body>
<div id="app">

    <input type="text" v-model:birthday="birthday"><br>
    <input type="text" v-model:birthday="user.name"><br>
    <input type="text" v-model:birthday="user.age">
</div>

<script type="text/javascript">
    var app = new Vue({
        el:"#app",
        data:{
            birthday:1616566607104,
            user:{"name":"java","age":1}
        },
        watch:{
            birthday(newValue,oldValue){
                console.log(newValue);
                console.log(oldValue);
            },
            user:{
                deep:true,
                handler(obj){
                    console.log(obj.name+"-"+obj.age);
                }
            }
        },
    });
</script>

</body>
</html>